1. Field of Use
This invention relates generally to mechanisms which enable components of a chair to be adjustably positioned relative to one another.
In particular, it relates to a backrest height adjustment mechanism which enables the backrest of a chair to be manually raised or lowered to a plurality of vertical positions relative to the chair seat and which releasably locks the backrest in a selected one of such positions.
2. Brief Description of the Prior Art
Prior art chair backrest height adjustment mechanisms of the aforesaid character take various forms. In some, a manually operable screw releasably secures a slidably adjustable backrest at desired positions on an upwardly extending J-bar which is part of the chair frame. In others, a manually operable rack-and-pinion type or ratchet type mechanism enables backrest height adjustment. Such prior mechanisms are typically relatively complex in constructions, costly to manufacture, trouble-prone, and unreliable in use. Protruding operating handles, levers or knobs are troublesome to manipulate or operate, and are visually unattractive and detract from the appearance of the chair.